We plan to continue our participation in cooperative clinical investigations of leukemia and cancer in children. This is accomplished by pooling the resources and patient material at this institution with the cooperative institutions forming Children's Cancer Group A for joint therapeutic studies of acute lymphocytic leukemia, non-lymphocytic leukemia, Wilms' Tumor, neuroblastoma, rhabdomyosarcoma, Ewing's sarcoma, histiocytosis X, osteogenic sarcoma, liver tumors and the evaluation of new agents in the treatment of childhood cancer. The specific protocols are those of Children's Cancer Group A.